This proposal is being submitted in response to Notice Number (NOT-OD-09-058) and Notice Title: NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications. Colon cancer, the second leading cause of cancer deaths for men and women in the United States, can be prevented if precursor colonic lesions are detected and removed. Virtual colonoscopy (VC), also known as computed tomographic colonography (CTC), Uhas been recently endorsed as a viable option for colorectal cancer screening in the new guideline. Non-cathartic CTC (ncCTC) is an emerging technique for eliminating rigorous cathartic cleansing from the bowel preparation used in current CTC. Electronic cleansing (EC) is a technique for removal of contrast-enhanced fecal materials in CTC images, effectively cleansing the colon after image acquisition to visualize the entire colonic mucosa. Computer-aided detection (CAD), which automatically detects polyps in CTC images, has the potential to detect polyps with high sensitivity and specificity, and to improve radiologists'polyp detection performance. The goals of the parent project was to develop and validate novel EC and CAD schemes for ncCTC, and to integrate them into the National Alliance of Medical Imaging Computing (NA-MIC) toolkit as computational modules, thereby developing a NA-MIC VC system. Since the time when the parent proposal was submitted and reviewed, two important advancements happened in the field of CTC. One is a wider availability of dual-energy and high-definition (high-resolution) CT scanners in clinical practice. The other is the recognition of the frequent occurrence of non-polypoid lesions and their clinical significance in colon cancer screening. Thus, the short-term goals of this proposal are to develop evaluate (1) an artifact-free EC scheme for non-cathartic dual energy CTC, which will effectively cleanse the residual fecal materials in the colon in CTC images of patients examined with non-cathartic bowel preparation and imaged with dual-energy CT scanner, and (2) a novel high-resolution CAD scheme for the detection of flat lesions in CTC. In a manner similar to the parent grant, they will be integrated into the NA-MIC toolkit to develop an advanced NA-MIC VC interpretation system. We hypothesize that the advanced NA-MIC VC system will allow artifact-free visualization of the mucosal surface of the colon, and improve radiologists'performance in the detection of non-polypoid lesions in ncCTC. To explore these hypotheses, we propose the following specific aims: Specific Aim 1: Develop dual-energy EC scheme. Specific Aim 2: Develop a high-resolution CAD scheme for the detection of non-polypoid lesions. Specific Aim 3: Validate the performance and benefit of the dual energy EC and CAD schemes. Successful development of the advanced NA-MIC VC system will provide a sophisticated platform consisting of tools for VC research as well as a VC interpretation system that can effectively be used for clinical trials. Such a VC platform will encourage new research efforts and provide impetus for research collaboration. The system also has the potential to provide a CT-based colorectal screening scheme of polypoid and non-polypoid lesions that will be highly acceptable to patients and highly accurate. Such a VC system will significantly advance the clinical implementation of CT-based colon cancer screening, promote the early diagnosis of colon cancer, and ultimately reduce the mortality due to colon cancer. PUBLIC HEALTH RELEVANCE: Successful development of the high-resolution CAD will substantially extend the NA-MIC VC system for providing a sophisticated platform consisting of tools for VC research as well as a VC system that can effectively be used for clinical trials. Such a VC platform will encourage new research efforts and provide impetus for research collaboration. The system also has the potential to provide a CT-based detection scheme of non-polypoid lesions that is highly acceptable to patients and highly accurate. Such a VC system will significantly advance the clinical implementation of CT-based colon cancer screening, promote the early diagnosis of colon cancer, and ultimately reduce the mortality due to colon cancer.